Thermophysical behaviour of matrix-grafted graphene/poly(ethylene tetrasulphide) nanocomposites
A novel approach was used to fabricate poly(ethylene tetrasulphide) (PETS)-modified graphene nanosheets. Accordingly, graphene oxide (GO) was modified with (3-chloropropyl)triethoxysilane (CPTES) to yield GO-Cl with the ability of participation in interfacial polymerization of 1,2-dichloromethane (EDC) and disodium tetrasulphide (Na2S4) and synthesis of graphene/PETS nanocomposites. Also, to investigate the effect of surface chemistry of the nanosheets on the properties of the nanocomposites, GO-Cl nanosheets were reduced by hydrazine monohydrate to obtain rGO-Cl. The success of modification and reduction of the nanosheets was confirmed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Then, two series of nanocomposites containing different contents of GO-Cl and rGO-Cl were synthesized. Proton nuclear magnetic resonance (1H NMR) was used to determine the molecular weights of the polymers. Also, dispersion of the nanosheets in the polymeric matrix was studied by XRD and thermal stability and the thermophysical properties of the nanocomposites were investigated by TGA and differential scanning calorimetry (DSC) respectively. Results showed that incorporation of the nanosheets leads to lower molecular weights of the polymeric matrix whereas reduced nanosheets were dispersed more appropriately in the matrix. According to the TGA results, the dispersion of nanosheets and molecular weight of the matrix were prominent factors in the thermal stability of the nanocomposites. Also, all samples showed a glass transition temperature (Tg) less than 0 °C, a cold crystallization temperature (Tcc), and a subsequent melting point (Tm) which were affected by the content of nanosheets.